The invention relates to an apparatus and method for enlarging the cross section of a chimney flue by removing wall material from the flue walls by means of a milling.
It is a constant task for chimney sweeps, boiler cleaners and other pipeline cleaning personnel to clean flue gas deposits out of exhaust gas pipes and to re-establish the original inner cross section of such pipes. This is sometimes done manually, sometimes by means of motor-driven servo supports. Even more stubborn deposits can be removed with relatively little effort so that generally brush-like cleaning tools and relatively weakly designed servo motors are sufficient. An example for cleaning flue gas pipes in a boiler system is disclosed in FR-A 2,074,527. In this prior art device, a cleaning brush is introduced into the boiler pipe to be cleaned together with a pneumatic motor driven by compressed air. The device here does not operate in the manner of a milling device but in the manner of a radial grinder (see also DE-A1 2,953,685 which works with a scrub brush).
Much more difficult is the cleaning of chimneys in old buildings in need of restoration. This is what the invention relates to exclusively.
The need for restoration may here have very different reasons. Thus, only as an example, the original pipe for carrying the flue gas may have become inoperable due to soot deposits, cracks, brittleness, permeability to flue gases, loss of thermal insulation or insufficient thermal insulation according to recent evaluations, or for other reasons. Or the inner lining layer that had been introduced in a first attempt at restoration may have been or become useless. Finally, in still properly operating chimney structures, a change in the inner cross section may be desired. In all these cases, a new inner pipe (called lining) for carrying the flue gas must be drawn into the chimney requiring the restoration, in certain cases so as to provide an additional radial space outside of this inner pipe to be drawn in, be it because of the necessity of introducing a thermal insulation layer at the same time, be it in order to provide space for some other purpose, for example for ventilation. Now the new inner pipe for carrying the flue gas must have a predetermined inner and thus also an outer diameter whose order of magnitude is predetermined, so that generally it is impossible to draw a new inner pipe for restoration into the already existing inner diameter of the chimney requiring the restoration. Therefore, it is necessary in all these cases to remove at least the present inner flue gas shell in the chimney requiring restoration before restoration pipe elements are inserted. In many cases of multi-shell chimney construction, the entire original inner flue gas carrying pipe will have to be removed. In other cases, as in the above-mentioned example of further restoration after a prior, failed restoration attempt, it may suffice to remove a centrifuged layer or the like, possibly together with edge zones of the original chimney structure.
Moreover, the materials of the interior pipes of existing chimneys and of the layers requiring restoration and being included therein are very different and almost always very resistant. Only as an example, older chimneys are constructed from natural or artificial stone, e.g. certain bricks, or are molded of concrete as single-shell molded pieces, particularly from concrete having thermal insulation properties. In more recent chimney constructions, the flue gas carrying interior pipes are often made of different quality fire clays up to glass, ceramic and high-grade steel pipes. In older chimneys, the lining of the inner pipe has also been formed of component similar to ceramic tiles.
Additionally, chimneys are not infrequently set in sections onto floor breakthroughs so that, for example, actual structural material such as, for example, concrete from floors or ceilings of rooms and reinforcement elements embedded therein, including iron reinforcements extend into the inner cross section of the flue gas carrying pipe in the region of the floor and often even form cross-sectional constrictions there. Corresponding cross-sectional constrictions are also frequently found if mortar work during the installation of the original chimney was not done very neatly.
Finally it has been found that quite a considerable percentage of the chimneys requiring restoration do not extend along a precisely vertical axis but, in individual cases, often exhibit surprising curvatures and crooked offsets.
It has already been considered to produce the required enlargement of the cross section of a chimney requiring restoration by means of a drill (reference numeral 6 in DE-U1 87 01 745.8; see also reference numeral 12 in DE-U1 86 26 492.3). However, drilling out chimneys is possible only if the inner layer is made of certain materials and is additionally undesirable because the chimney structure is subjected to uncontrollable pressure influences. The only thing in favor of drilling is a relatively favorable operating speed.
Less stress on the chimney structure is realized with grinding. This, however, is connected with a considerable amount of time. If, moreover, the rotary grinding tools employed are those equipped with flying chains as disclosed in SE-C 177,343 or SE-C 177,783, there additionally occur washboard-like groove formations at the interior surface of the chimney. This applies also if these flying chains are arranged as taught in WO 86 00 391 issued by WIPO in immediately axially successive planes of the rotary tool; this merely makes the washboard effect more compact.
If a milling cutter is employed, however, the existing chimney structure is treated gently and a high operating speed can be realized. This is connected with tool geometries that can be employed in greater multitudes and thus there is better adaptability, on the one hand, to existing conditions and, on the other hand, to the work goal.
In addition to the stated methods of widening the inner width of a chimney in need of restoration by drilling, grinding or milling, it is also known to provide a tool which performs a hammering action. Thus, U.S. Pat. No. 4,603,747 discloses a rotating vibratory hammer. However, such a hammer is suitable only for special cases, here to chip off the tiles serving as the inner lining of the flue gas pipe.
Finally, it is known to cause a rotary tool for widening the inner cross section of a chimney requiring restoration to perform axial striking oscillations by way of a striking mechanism. This also, however, leads to undesirable shocks to the chimney structure (AT-A 325,290).
The invention is based on AT-A 203,707 in which, in addition to the use of grinding or hammering tools, milling cutters have also been considered. The respective grinding tool or milling cutter in this prior art device together with its drive motor can be moved up and down chimney flue.
The invention prefers the use of actual milling cutters. Insofar as the term milling cutters is used here, they may also be replaced, particularly for special applications or additional process steps, by drilling or grinding tools which are included in the term material removing tools.
This prior art device differs from more remote devices in which the drive motor is disposed outside of the chimney and torque is transmitted into the interior of the chimney by way of a possibly flexible shaft (see DE-A 1,229,230, WO 86/00391 issued by WIPO).
Due to the limited length available for the torque transmitting shaft in such devices, the drive must be accommodated on the roof, with a range greater than about 10 meters being possible only by the further coupling in of flexible extension shafts and a loss of power. In this connection, it has been found to be possible to start the drive motor only if a tool is used to remove the end piece of the shaft from the chimney. The flexible shaft and the tool thus move out in the open and constitute a grave danger for the operating personnel Moreover, the shafts and their connecting couplings quickly wear out in operation and additionally tend to break suddenly. Generally, their manipulation is fraught with problems. Use in chimneys that are not axially linear is possible only very conditionally.
However, AT-A 203,707 provides an electric motor drive. In a preferred embodiment of this prior art device, the stator of the electric motor simultaneously serves as a guide for the motor along the interior wall of the chimney. In all disclosed embodiments, the amount of apparatus required and the minimum diameter of the device connected therewith is so large that the device does not appear to be suitable for drilling chimneys having a rated diameter of less than 150 mm. And it appears to be particularly impossible to pass such a device through the inner cross section of a chimney of this rated diameter in order to then mill from the bottom to the top when there are additional interior deposits.
Moreover, electric motor drives do not appear suitable at all for introduction into a chimney. Only as examples, reference shall be made to the danger of explosion in deposited soot if a spark is generated, the danger of electrical short circuits at conductive regions of the interior wall of the chimney (e.g. projecting metal reinforcements or due to soot deposits on regions that have become conductive due to the presence of liquids), the danger of combustion due to the motor running hot because of insufficient ventilation if the additional space requirement for liquid cooling is avoided, the danger of an accident to operating personnel, the heavy operating weight, the infrequent availability of heavy current at the work location and the like. Additionally, milling cutters driven by electric motors tend to seize up in the masonry even if, as in the case of the above-mentioned AT-A 203,707, counteracting decoupling devices are provided. Further, a sensitive infinite regulation is possible only with difficulties. Finally, the entire apparatus completely covers the viewing cross section of the chimney so that direct observation of the milling process from the upper chimney opening is impossible. Viewing from below is out of the question, primarily because of the dropping down of material loosened by the milling.
Inasmuch as can be determined, electric motors lowered into the chimney together with the milling cutter have not found acceptance in practice, probably for the reasons mentioned above. Not without reason is the electric motor disclosed and employed in the case of WO 86/00391 issued by WIPO also disposed outside of the chimney and the costs of connecting this electric motor by way of flexible rod assemblies with the rotary tool, in this case a chain grinder, disposed in the interior of the chimney are considered inevitable.